#ifndef VEC3_H
#define VEC3_H



class vec3 {
public:
		
	double	e[3];

	vec3():e{ 0,0,0 } {}

	vec3(double e0,double e1,double e2): e{e0,e1,e2} {}

	double x() const { return e[0]; }
	double y() const { return e[1]; }
	double z() const { return e[2]; }

	vec3 operator-() const { return vec3(-e[0], -e[1], -e[2]); }
	double operator[](int i) const { return e[i]; }
	double& operator[](int i) { return e[i]; }

	vec3& operator+=(const vec3& v) {
		e[0] += v.e[0];
		e[1] += v.e[1];
		e[2] += v.e[2];
		return *this;
	}

	vec3& operator*=(double t) {
		e[0] *= t;
		e[1] *= t;
		e[2] *= t;
		return *this;
	}

	vec3& operator/=(double t) {
		return *this *= 1 / t;
	}

	double length() const {
		return std::sqrt(length_squared());
	}

	double length_squared() const {
		return e[0] * e[0] + e[1] * e[1] + e[2] * e[2];
	}

	bool near_zero() const {
		// deal with near zero vector
		auto s = 1e-8;
		return (std::fabs(e[0]) < s) && (std::fabs(e[1]) < s) && (std::fabs(e[2]) < s);
	}


	static vec3 random() {
		return vec3(random_double(), random_double(), random_double());
	}

	static vec3 random(double min,double max) {
		return vec3(random_double(min,max), random_double(min, max), random_double(min, max));
	}



};



//point3 is same as vec3
using point3 = vec3;


inline std::ostream& operator<<(std::ostream& out, const vec3& v) {
	return out << v.e[0] << ' ' << v.e[1] << ' ' << v.e[2];
}

inline vec3 operator+(const vec3& u, const vec3& v) {
	return vec3(u.e[0] + v.e[0], u.e[1] + v.e[1], u.e[2] + v.e[2]);
}

inline vec3 operator-(const vec3& u, const vec3& v) {
	return vec3(u.e[0] - v.e[0], u.e[1] - v.e[1], u.e[2] - v.e[2]);
}

inline vec3 operator*(const vec3& u, const vec3& v) {
	return vec3(u.e[0] * v.e[0], u.e[1] * v.e[1], u.e[2] * v.e[2]);
}

inline vec3 operator*(double t, const vec3& v) {
	return vec3(t * v.e[0], t * v.e[1], t * v.e[2]);
}

inline vec3 operator*(const vec3& v, double t) {
	return t*v;
}

inline vec3 operator/(const vec3& v, double t) {
	return (1/t) * v;
}

inline double dot(const vec3& u, const vec3& v) {
	return u.e[0] * v.e[0] + u.e[1] * v.e[1] + u.e[2] * v.e[2];
}

inline vec3 cross(const vec3& u, const vec3& v) {
	return vec3(u.e[1]*v.e[2]- u.e[2] * v.e[1], u.e[2] * v.e[0] - u.e[0] * v.e[2], u.e[0] * v.e[1] - u.e[1] * v.e[0]);
}

inline vec3 unit_vector(const vec3& v) {
	return v / v.length();
}

inline vec3 random_in_unit_disk() {
	while (true) {
		auto v = vec3(random_double(-1,1), random_double(-1,1), 0);
		if (v.length_squared() < 1) return v;
	}
}




inline vec3 random_unit_vector() {
	while (true) {
		auto p = vec3::random(-1, 1);
		auto lsq = p.length_squared();
		if (1e-160<=lsq&&lsq <= 1.0) {
			return p / sqrt(lsq);
		}
	}
}

inline vec3 random_on_hemisphere(const vec3& norm) {
	vec3 randvec = random_unit_vector();
	if (dot(randvec, norm) > 0.0) {
		return randvec;
	}
	else {
		return -randvec;
	}
}




inline vec3 reflect(const vec3& v, const vec3& n) {
	return v - 2 * dot(v, n) * n;
}

inline vec3 refract(const vec3& uv, const vec3 n, double eta_etap) {
	auto cos_theta = std::fmin(dot(-uv, n), 1.0);
	vec3 r_out_perp = eta_etap * (uv + cos_theta * n);
	vec3 r_out_parallel = -std::sqrt(std::fabs(1.0 - r_out_perp.length_squared())) * n;
	
	return r_out_perp + r_out_parallel;
}













#endif
